Question

A right circular cylinder is changing shape. The radius is decreasing at the rate of 2 inches/sec while it's height is increasing at the rate of 5 inches/sec. When the radius is 4 inches and the height is 6 inches, how fast is the volume changing? Round your answer to three decimal places

Answer 1

Answer:

552.640in³/s

Step-by-step explanation:

Volume of a cylinder is expressed as;

$V = \pi r^2 h$

$\frac{dV}{dt} = \frac{dV}{dr} \frac{dr}{dt} +\frac{dV}{dh} \frac{dh}{dt}$

dV/dr = 2πrh

dV/dr = 2π(4)(6)

dV/dr = 48(3.14)

dV/dr = 150.72in³/m

dV/dh = πr²

dV/dh = 3.14(4)²

dV/dh = 50.24

Given

dh/dt = 5in/s

dr/dt = 2in/s

Substitute into the dV/dt

dV/dt = 150.72(2)+50.24(5)

dV/dt = 301.44 + 251.2

dV/dt= 552.640in³/s

The volume is changing at the rate of  552.640in³/s